An envelope usually made of paper or plastic material which permits steam and heat penetration and the exhaustion of air in the sterilization process. It may be self or heat sealed. It is used in the sterilization of syringes, needles, small surgical instruments, pipettes and the like. Excludes BAG, STERILIZATION; BAG, STERILIZATION-BIOHAZARD DISPOSAL; and WRAPPER, STERILIZATION.